Solid-state imaging device, manufacturing method thereof, and electronic apparatus

ABSTRACT

A solid-state imaging device includes a plurality of photoelectric conversion portions each provided in a semiconductor substrate and receives incident light through a light sensing surface, and a pixel separation portion provided to electrically separate a plurality of pixels. At least a pinning layer and a light shielding layer are provided in an inner portion of a trench provided on a side portion of each of the photoelectric conversion portions in an incident surface side, the trench includes a first trench and a second trench formed to be wider than the first trench in a portion shallower than the first trench, the pinning layer is formed in an inner portion of the first trench to cover an inside surface of the second trench, and the light shielding layer is formed to bury an inner portion of the second trench at least via the pinning layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/830,246, filed Dec. 4, 2017, which is a continuation of U.S. patentapplication Ser. No. 15/407,381, filed Jan. 17, 2017, now U.S. Pat. No.9,871,071, which is a continuation of U.S. patent application Ser. No.15/239,679, filed Aug. 17, 2016, now U.S. Pat. No. 9,576,996, which is acontinuation of U.S. patent application Ser. No. 15/084,738, filed Mar.30, 2016, now U.S. Pat. No. 9,490,293, which is a continuation of U.S.patent application Ser. No. 14/573,904, filed Dec. 17, 2014, now U.S.Pat. No. 9,577,002, which is a continuation of U.S. patent applicationSer. No. 13/370,412, filed Feb. 10, 2012, now U.S. Pat. No. 8,941,198,which claims priority to Japanese Patent Application No. JP 2011-040531,filed in the Japan Patent Office on Feb. 25, 2011, the entiredisclosures of which are hereby incorporated herein by reference.

BACKGROUND

The present disclosure relates to a solid-state imaging device, amanufacturing method thereof, and an electronic apparatus.

Electronic apparatuses such as a digital video camera or a digital stillcamera include a solid-state imaging device. For example, thesolid-state imaging device includes a CMOS (Complementary Metal OxideSemiconductor) type image sensor or a CCD (Charge Coupled Device) typeimage sensor.

In the solid-state imaging device, a plurality of pixels are arranged ona pixel region of a substrate. A photoelectric conversion portion isprovided on each pixel. For example, the photoelectric conversionportion is a photodiode, and receives incident light through the lightsensing surface and generates a signal charge by performing aphotoelectric conversion with respect to the received light.

Among the solid-state imaging devices, in the CCD type image sensor, avertical transfer portion is provided between a plurality of pixelcolumns which are vertically lined up in a pixel region. In the verticaltransfer portion, a plurality of transfer electrodes are provided so asto be facing a vertical channel region through gate insulating films,and the vertical transfer portion is configured so as to transfer thesignal charge, which is read from the photoelectric conversion portionby a charge readout portion, in a vertical direction.

In contrast, in the CMOS type image sensor, pixels are configured so asto include a pixel transistor in addition to the photoelectricconversion portion. The pixel transistor is configured so as to read thesignal charge generated by the photoelectric conversion portion andoutput the read signal charge to a signal line as an electric signal.

In general, the solid-state imaging device is provided on a frontsurface side in which a multilayer wiring layer on which a plurality ofwirings are laminated is provided in a substrate, and a photoelectricconversion portion receives light incident from the front surface sidethrough a light sensing surface.

In the case of the “front surface illumination type”, the thickmultilayer wiring layer is disposed between a microlens and the lightsensing surface. Thereby, when light enters in an inclined state withrespect to the light sensing surface, the light is shielded by thewirings included in the multilayer wiring layer, and the light may notreach the light sensing surface JS. In addition, the incident light dosenot enter the photodiode of the pixel just below the light, and mayenter the photodiodes of other pixels. Thereby, disadvantages such asshading or a color mixing may be generated in the captured image.Moreover, besides this, it may be difficult to improve sensitivity.

Therefore, “a rear surface illumination type” has been suggested inwhich the photoelectric conversion portion receives the light incidentfrom a rear surface side which is a side opposite to the front surfaceon which the multilayer wiring layer is provided in the substrate.However, also in the “rear surface illumination type”, the incidentlight entering one pixel may not enter the photodiode of this one pixeland enter photodiodes of the adjacent other pixels. Thereby, noise isincluded in the signal due to the optical phenomenon, a disadvantagesuch as “color mixing” is generated in the captured image, and qualityof the captured image may be decreased. In order to suppress occurrenceof the disadvantage, light shielding films are provided between aplurality of pixels (for example, refer to Japanese Unexamined PatentApplication Publication Nos. 2010-109295 and 2010-186818).

Moreover, in the solid-state imaging device, in order to suppress a darkcurrent from being generated due to an interface state of thesemiconductor substrate on which the photoelectric conversion portion isprovided, the photoelectric conversion portion including an HAD (HoleAccumulation Diode) structure has been suggested. In the HAD structure,since a positive charge (hole) accumulation region is formed on thelight sensing surface of a n-type charge accumulation region, occurrenceof the dark current is suppressed.

In addition, in order to form the positive charge accumulation region inthe interface portion of the photoelectric conversion portion,suppressing occurrence of the dark current by providing “a film having anegative fixed charge” as a pinning layer has been suggested. Forexample, a high dielectric constant film such as a hafnium oxide film(HfO₂ film) may be used as the “film having a negative fixed charge”(for example, refer to Japanese Unexamined Patent ApplicationPublication No. 2008-306154 or the like).

Moreover, in the solid-state imaging device, in order to prevent thesignals output from each pixel from being mixed by electric noise, apixel separation portion which electrically separates a plurality ofpixels is provided. For example, a high concentration impurity region,which is formed by ion-implanting impurities of a high concentration tothe semiconductor substrate, is provided on the pixel separationportion.

SUMMARY

FIG. 23 is a cross-sectional diagram illustrating main portions of apixel P in the CMOS image sensor of the “rear surface illuminationtype”.

As illustrated in FIG. 23, in the CMOS image sensor of the “rear surfaceillumination type”, a photodiode 21 is provided in a portion which isdivided by a pixel separation portion 101 pb in the inner portion of asemiconductor substrate 101. In the photodiode 21, an n-typesemiconductor region 101 n is formed as a charge accumulation region.The photodiode 21 is an HAD structure, and the n-type semiconductorregion 101 n is formed so as to be interposed between p-typesemiconductor regions 101 pa and 101 pc in the depth direction z of thesemiconductor substrate 101. In addition, the pixel separation portion101 pb is formed by ion-implanting p-type impurities with highconcentration to the semiconductor substrate 101.

Although not illustrated in FIG. 23, a pixel transistor is provided onthe front surface (lower surface in FIG. 23) of the semiconductorsubstrate 101, and as illustrated in FIG. 23, a wiring layer 111 isprovided so as to cover the pixel transistor. The wiring layer 111 isformed so that wirings 111 h are covered by an insulating layer 111 z.In addition, a supporting substrate SS is provided on the front surface(lower surface) of the wiring layer 111.

In contrast, a light shielding film 60, a color filter CF, and amicrolens ML are provided on the rear surface (upper surface in FIG. 23)of the semiconductor substrate 101, and the photodiode 21 receives theincident light H which enters via each of the portions.

Here, as illustrated in FIG. 23, for example, the light shielding film60 is formed on the upper surface of the semiconductor substrate 101 viaan insulating film SZ which is a silicon oxide film. The light shieldingfilm 60 is provided above the pixel separation portion 101 pb providedin the inner portion of the semiconductor substrate 101. For example,the light shielding film 60 is formed by using a light shieldingmaterial such as metal.

Moreover, the upper surface of the light shielding film 60 is covered bya planarized film HT, and the color filter CF and the microlens ML areprovided on the upper surface of the planarized film HT. For example, inthe color filter CF, each filter layer of three primary colors isarranged for each pixel P in a Bayer array.

However, in the case of the above-described configuration, in order tothe light shielding film 60, the distance between the light sensingsurface JS and the microlens ML becomes longer. Thereby, a focusingproperty of the microlens ML may be deteriorated, and quality of thecaptured image may be decreased.

Moreover, although the light shielding film 60 is formed, since theincident light H entering one pixel P is transmitted below the lightshielding film 60 and enters the photodiodes 21 of the adjacent otherpixels P, quality of the captured image may be decreased.

Particularly, when the incident light H enters in a largely inclinedstate, the incident light H may pass through the pixel separationportion 101 pb which is formed by the ion implantation of impuritieshaving a high concentration and may enter the photodiodes 21 of theadjacent other pixels P. Thereby, a so-called “color mixing” may begenerated, and color reproducibility in the captured color image may bedecreased. In addition, quality of the captured image may be decreaseddue to occurrence of the “shading”.

In this way, in the solid-state imaging device, it may be difficult tosufficiently improve quality of the captured image due to occurrence ofoptical noise by leakage of the inclined light.

Besides this, when the pixel separation portion 101 pb is formed byion-implanting impurities, the width of the pixel separation portion 101pb is widened with consideration for diffusion of the impurities or thelike. Thereby, it may be difficult to widen the occupancy area of thephotodiode 21. Therefore, a saturation charge accumulation amount (Qs)of the photodiode 21 is decreased, and it may be difficult to improvethe quality of the captured image.

The above described disadvantages are not limited to the case of the“rear surface illumination type” and may be also generated in the caseof the “front surface illumination type” solid-state imaging device.

In this way, in the solid-state imaging device, it may be difficult toimprove quality of the captured image due to various factors.

Therefore, it is desirable to provide a solid-state imaging device, amanufacturing method thereof, and an electronic apparatus capable ofimproving quality or the like of a captured image.

According to an embodiment of the present disclosure, there are provideda solid-state imaging device and an electronic apparatus which include aplurality of photoelectric conversion portions each provided tocorrespond to each of a plurality of pixels in a semiconductor substrateand receives incident light through a light sensing surface, and a pixelseparation portion that is provided between the plurality of pixels inan inner portion of the semiconductor substrate and electricallyseparates the plurality of pixels, wherein at least a pinning layer anda light shielding layer are provided in an inner portion of a trenchwhich is provided on a side portion of each of the photoelectricconversion portions in an incident surface side of the semiconductorsubstrate into which the incident light enters, the trench includes afirst trench and a second trench having a width wider than that of thefirst trench in a portion shallower than the first trench in thesemiconductor substrate, the pinning layer is formed in an inner portionof the first trench so as to cover an inside surface of the secondtrench, and the light shielding layer is formed so as to bury an innerportion of the second trench at least via the pinning layer.

According to another embodiment of the present disclosure, there isprovided a method of manufacturing a solid-state imaging device whichincludes providing a plurality of photoelectric conversion portionswhich receive incident light through a light sensing surface so as tocorrespond to a plurality of pixels in a semiconductor substrate, andforming a pixel separation portion, which electrically separates theplurality of pixels, between the plurality of pixels in an inner portionof the semiconductor substrate, the forming of the pixel separationincludes providing at least a pinning layer and a light shielding layerin an inner portion of a trench which is provided on a side portion ofeach of the photoelectric conversion portions in an incident surfaceside of the semiconductor substrate into which the incident lightenters, a first trench and a second trench having a width wider thanthat of the first trench in a portion shallower than the first trench inthe semiconductor substrate are formed as the trench, the pinning layeris formed so as to cover an inner portion of the first trench and aninside surface of the second trench, and the light shielding layer isformed so as to bury an inner portion of the second trench at least viathe pinning layer.

According to the embodiments of the present disclosure, the first trenchand the second trench having the width wider than that of the firsttrench in the portion shallower than the first trench in thesemiconductor substrate are formed as the trench in the pixel separationportion. Moreover, the pinning layer is formed in an inner portion ofthe first trench so as to cover an inside surface of the second trench.In addition, the light shielding layer is formed so as to bury an innerportion of the second trench at least via the pinning layer. Byconfiguring the pixel separation portion in this way, the pixelseparation portion electrically and optically separates the plurality ofpixels.

According to the present disclosure, it is possible to provide asolid-state imaging device, a manufacturing method thereof, and anelectronic apparatus capable of improving quality or the like of thecaptured image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram illustrating a configuration of acamera in a first embodiment.

FIG. 2 is a diagram illustrating the entire configuration of asolid-state imaging device in the first embodiment.

FIG. 3 is a diagram illustrating main portions of the solid-stateimaging device in the first embodiment.

FIG. 4 is a diagram illustrating main portions of the solid-stateimaging device in the first embodiment.

FIG. 5 is a diagram illustrating main portions of the solid-stateimaging device in the first embodiment.

FIG. 6 is a timing chart illustrating a control signal which is sent toa pixel transistor of a pixel when performing an imaging in the firstembodiment.

FIG. 7 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the first embodiment.

FIG. 8 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the first embodiment.

FIG. 9 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the first embodiment.

FIG. 10 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the first embodiment.

FIG. 11 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the first embodiment.

FIG. 12 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the first embodiment.

FIG. 13 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the first embodiment.

FIG. 14 is a diagram illustrating the method of manufacturing asolid-state imaging device in a second embodiment.

FIG. 15 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the second embodiment.

FIG. 16 is a diagram illustrating main portions of a solid-state imagingdevice in a third embodiment.

FIG. 17 is a diagram illustrating the method of manufacturing thesolid-state imaging device in the third embodiment.

FIG. 18 is a diagram illustrating the method of manufacturing asolid-state imaging device in the third embodiment.

FIG. 19 is a diagram illustrating main portions of a solid-state imagingdevice in a fourth embodiment.

FIG. 20 is a diagram illustrating the main portions of the solid-stateimaging device in the fourth embodiment.

FIG. 21 is a diagram illustrating the main portions of the solid-stateimaging device in the fourth embodiment.

FIG. 22 is a diagram illustrating main portions of a solid-state imagingdevice in a fifth embodiment.

FIG. 23 is a cross-sectional diagram illustrating main portions of apixel P in a CMOS image sensor of “a rear surface illumination type”.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described with referenceto the drawings.

In addition, description is performed in the following order.

1. First Embodiment (Case of Rear Surface Illumination

Type)

2. Second Embodiment (Case Where Manufacturing Method is PartiallyDifferent from First Embodiment)

3. Third Embodiment (Case Where Insulating film and Pinning Layer areProvided in Trench of Lower Portion)

4. Fourth Embodiment (Case Where Depth of Trench is Different Accordingto Wavelength of Received Light)

5. Fifth Embodiment (Case of Front Surface Illumination

Type)

6. Others

1. First Embodiment

(A) Apparatus Configuration

(A-1) Main Portion Configuration of Camera

FIG. 1 is a configuration diagram illustrating a configuration of acamera 40 in a first embodiment.

As illustrated in FIG. 1, the camera 40 includes a solid-state imagingdevice 1, an optical system 42, a control portion 43, and a signalprocessing portion 44. Each portion will be sequentially described.

The solid-state imaging device 1 receives incident light H, which entersas a subject image via the optical system 42, through an imaging surfacePS, performs a photoelectric conversion with respect to the receivedlight, and generates a signal charge. Here, the solid-state imagingdevice 1 reads the signal charge by being driven based on a controlsignal output from the control portion 43, and outputs an electricsignal.

The optical system 42 includes optical members such as an imaging lensor an aperture and is disposed so as to focus the incident light H onthe imaging surface PS of the solid-state imaging device 1.

The control portion 43 outputs various control signals to thesolid-state imaging device 1 and the signal processing portion 44, andcontrols and drives the solid-state imaging device 1 and the signalprocessing portion 44.

The signal processing portion 44 is configured so as to generate adigital image with respect to the subject image by performing a signalprocessing while having the electric signal output from the solid-stateimaging device 1 as a raw data.

(A-2) Main Portion Configuration of Solid-state Imaging Device

The entire configuration of the solid-state imaging device 1 will bedescribed.

FIG. 2 is a diagram illustrating the entire configuration of asolid-state imaging device 1 in a first embodiment of the presentdisclosure.

The solid-state imaging device 1 of the present embodiment is a CMOStype image sensor and includes a semiconductor substrate 101 asillustrated in FIG. 2. For example, the semiconductor substrate 101 maybe formed by thinning a single crystal silicon semiconductor substrate,and a pixel region PA and a peripheral region SA are provided on thesurface of the semiconductor substrate.

As illustrated in FIG. 2, the pixel region PA is a rectangular shape,and a plurality of pixels P are disposed in each of a horizontaldirection x and a vertical direction y. That is, the pixels P are linedup with a matrix form.

In the pixel region PA, the pixels P are configured so as to receive theincident light and generate the signal charge. Moreover, the generatedsignal charge is read by a pixel transistor (not illustrated) and outputas an electric signal. The detailed configuration of the pixels P willbe described hereinafter.

As illustrated in FIG. 2, the peripheral region SA is positioned in theperiphery of the pixel region PA. Moreover, a peripheral circuit isprovided in the peripheral region SA.

Specifically, as illustrated in FIG. 2, a vertical drive circuit 13, acolumn circuit 14, a horizontal drive circuit 15, an external outputcircuit 17, a timing generator (TG) 18, and a shutter drive circuit 19are provided as the peripheral circuit.

As illustrated in FIG. 2, the vertical drive circuit 13 is provided atthe side portion of the pixel region PA in the peripheral region SA, andthe vertical drive circuit is configured so as to select and drive thepixels P of the pixel region PA by a row unit.

As illustrated in FIG. 2, the column circuit 14 is provided at the lowerend of the pixel region PA in the peripheral region SA, and performs asignal processing with respect to the signal which is output from thepixels P by a column unit. Here, the column circuit 14 includes a CDS(Correlated Double Sampling) circuit (not illustrated) and performs asignal processing which removes a fixed pattern noise.

As illustrated in FIG. 2, the horizontal drive circuit 15 iselectrically connected to the column circuit 14. For example, thehorizontal drive circuit 15 includes a shift register and sequentiallyoutputs the signal, which is held for each column of the pixels P in thecolumn circuit 14, to the external output circuit 17.

As illustrated in FIG. 2, the external output circuit 17 is electricallyconnected to the column circuit 14. In addition, after the externaloutput circuit 17 performs a signal processing with respect to thesignal output from the column circuit 14, the external output circuitoutputs the processed signal to the external. The external outputcircuit 17 includes an AGC (Automatic Gain Control) circuit 17 a and anADC circuit 17 b. In the external output circuit 17, after the AGCcircuit 17 a multiplies the signal by a gain, the ADC circuit 17 bconverts the analog signal to the digital signal and outputs theconverted signal to the external.

As illustrated in FIG. 2, the timing generator 18 is electricallyconnected to the vertical drive circuit 13, the column circuit 14, thehorizontal drive circuit 15, the external output circuit 17, and theshutter drive circuit 19 respectively. The timing generator 18 generatesvarious timing signals, outputs the signals to the vertical drivecircuit 13, the column circuit 14, the horizontal drive circuit 15, theexternal output circuit 17, and the shutter drive circuit 19. Therefore,the timing generator performs the driving control with respect to eachportion.

The shutter drive circuit 19 is configured so as to select the pixels Pby a row unit and adjust an exposure time in the pixels P.

(A-3) Detailed Configuration of Solid-state Imaging Device

The detailed contents of the solid-state imaging device according to thepresent embodiment are described.

FIGS. 3 to 5 are diagrams illustrating main portions of the solid-stateimaging device in a first embodiment.

FIG. 3 is a cross-sectional diagram of the pixel P. Moreover, FIG. 4 isa top view of the pixel P. In addition, FIG. 5 illustrates a circuitconfiguration of the pixel P. Moreover, FIG. 3 illustrates across-section taken along a line III-III illustrated in FIG. 4.Moreover, in FIG. 4, for convenience of description, in some cases,portions which illustrate each member are denoted by a broken line orthe like other than a solid line.

As illustrated in FIG. 3, the solid-state imaging device 1 includes aphotodiode 21 and a pixel separation portion 301 in the inner portion ofthe semiconductor substrate 101. Here, each portion is provided in thesemiconductor substrate 101 of thinned single crystal silicon.

Members such as a color filter CF and a microlens ML are provided on arear surface (upper surface in FIG. 3) of the semiconductor substrate101.

In contrast, although not illustrated in FIG. 3, a pixel transistor Trillustrated in FIG. 5 is provided on the front surface (lower surface inFIG. 3) of the semiconductor substrate 101. Moreover, as illustrated inFIG. 3, a wiring layer 111 is provided so as to cover the pixeltransistor Tr. In addition, in the wiring layer 111, a supportingsubstrate SS is provided on the surface of the side opposite to the sideof the semiconductor substrate 101.

That is, the solid-state imaging device 1 of the present embodiment is a“rear surface illumination type CMOS image sensor”, and is configured sothat the photodiode 21 receives the light H incident from the rearsurface (upper surface) and generates a color image by imaging.

Details of each portion will be sequentially described.

(a) Photodiode 21

In the solid-state imaging device 1, a plurality of photodiodes 21 aredisposed in the pixel region PA so as to correspond to the plurality ofpixels P illustrated in FIG. 2. That is, the plurality of photodiodes 21are provided so as to be lined up in each of a horizontal direction xand a vertical direction y perpendicular to the horizontal direction xin an imaging surface (xy plan).

The photodiode 21 is configured so as to generate signal charge byreceiving the incident light H and performing a photoelectric conversionof the received light and accumulate the generated signal charge.

Here, as illustrated in FIG. 3, the photodiode 21 receives the light Hincident from the rear surface (upper surface in FIG. 3) side of thesemiconductor substrate 101. As illustrated in FIG. 3, a planarized filmHT, a color filter CF and a microlens ML are provided above thephotodiode 21, the incident light H, which enters sequentially via eachportion, is received through a light sensing surface JS, and aphotoelectric conversion of the received light is performed.

As illustrated in FIG. 3, the photodiode 21 is provided in thesemiconductor substrate 101.

For example, the photodiode 21 is formed as a charge accumulation regionin which an n-type semiconductor region 101 n accumulates a charge(electrons). In the photodiode 21, the n-type semiconductor region 101 nis provided in the inner portion of p-type semiconductor regions 101 paand 101 pc of the semiconductor substrate 101. Here, in the n-typesemiconductor region 101 n, the p-type semiconductor region 101 pc,which has a higher impurity concentration than the rear surface (uppersurface) side, is provided in the front surface (lower surface) side ofthe semiconductor substrate 101. That is, the photodiode 21 is an HADstructure, and the p-type semiconductor regions 101 pa and 101 pc areformed in each interface of the upper surface side and the lower surfaceside of the n-type semiconductor region 101 n in order to suppressoccurrence of a dark current.

As illustrated in FIG. 3, a pixel separation portion 301 whichelectrically separates the plurality of pixels P is provided in theinner portion of the semiconductor substrate 101, and the photodiode 21is provided in the region of the pixel P which is divided by the pixelseparation portion 301. For example, as illustrated in FIG. 4, the pixelseparation portion 301 is formed in a lattice shape so as to beinterposed between the plurality of pixels P, and the photodiode 21 isformed in the region of the pixel P which is divided by the pixelseparation portion 101 pb.

In addition, as illustrated in FIG. 5, an anode is grounded to eachphotodiode 21, and each photodiode 21 is configured so that theaccumulated signal charge (here, electrons) is read by a pixeltransistor Tr and output to a vertical signal line 27 as an electricsignal.

(b) Color Filter CF

In the solid-state imaging device 1, as illustrated in FIG. 3, the colorfilter CF is provided on the rear surface (upper surface in FIG. 3) sideof the semiconductor substrate 101.

As illustrated in FIG. 4, the color filter CF includes a red filterlayer CFR, a green filter layer CFG, and a blue filter layer CFB. Eachof the red filter layer CFR, the green filter layer CFG, and the bluefilter layer CFB is disposed so as to be adjacent to one another, andthe layers are all provided so as to correspond to each of the pluralityof pixels P.

Here, as illustrated in FIG. 4, each of the red filter layer CFR, thegreen filter layer CFG, and the blue filter layer CFB is disposed so asto be lined up by Bayer array. That is, a plurality of green filterlayers CFG are disposed so as to be lined up in the diagonal directionto be a checked pattern. Moreover, the red filter layer CFR and the bluefilter layer CFB are disposed so as to be lined up in the diagonaldirection in the plurality of green filter layers CFG.

In the color filter CF, the red filter layer CFR has a higher lighttransmissivity at a wavelength band (for example, 625 to 740 nm)corresponding to red. That is, the red filter layer CFR is formed sothat the incident light H is colored red and transmitted to the lightsensing surface JS.

Moreover, in the color filter CF, the green filter layer CFG has ahigher light transmissivity at a wavelength band (for example, 500 to565 nm) corresponding to green. That is, the green filter layer CFG isformed so as to have a higher light transmissivity with respect to thelight of the wavelength range of the shorter wavelength than thewavelength having the higher light transmissivity in the red filterlayer CFR, and to color the incident light H green and transmit thecolored light to the light sensing surface JS.

In addition, in the color filter CF, the blue filter layer CFB has ahigher light transmissivity in a wavelength band (for example, 450 to485 nm) corresponding to blue. That is, the blue filter layer CFG isformed so as to have a higher light transmissivity with respect to thelight of the wavelength range of the shorter wavelength than thewavelength having the higher light transmissivity in the green filterlayer CFG, and to color the incident light blue and transmit the coloredlight to the light sensing surface JS.

In this way, in the color filter CF, a plurality of kinds of filterlayers CFR, CFG, and CFB having a higher transmissivity in light ofwavelength ranges different from one another are disposed so as to beadjacent to one another corresponding to each of the plurality of pixelsP.

(c) Microlens ML

In the solid-state imaging device 1, as illustrated in FIG. 3, themicrolens ML is provided on the upper surface of the color filter CF inthe rear surface (upper surface in FIG. 3) side of the semiconductorsubstrate 101.

A plurality of microlenses ML are disposed so as to correspond to eachpixel P. The microlens ML is a convex lens which is protruded in aconvex shape in the rear surface side of the semiconductor substrate101, and is configured so as to focus the incident light H to thephotodiode 21 of each pixel P. For example, the microlens ML is formedby using an organic material such as a resin.

(d) Pixel Separation Portion 301

In the solid-state imaging device 1, as illustrated in FIGS. 3 and 4,the pixel separation portion 301 is formed so as to divide between theplurality of pixels P in the inner portion of the semiconductorsubstrate 101. In addition, the pixel separation portion 301electrically separates the plurality of pixels P. That is, the pixelseparation portion electrically separates the photodiodes 21 of eachpixel P.

As illustrated in FIG. 3, in the pixel separation portion 301 positionedbetween the plurality of pixels P, the p-type semiconductor regions 101pa and 101 pc are provided between the n-type semiconductor regions 101n which configure the charge accumulation region of the photodiode 21.

Moreover, as illustrated in FIG. 3, a trench TR is provided at a portionwhich is positioned in the side portion of the photodiode 21 in the sideof the rear surface (upper surface) into which the incident light Henters in the semiconductor substrate 101.

Specifically, as illustrated in FIG. 3, the trench TR is formed so as toinclude a first trench TR1 and a second trench TR2.

Here, the first trench TR1 is provided in the deeper portion in thesemiconductor substrate 101.

In addition, the second trench TR2 is disposed in the portion shallowerthan the first trench TR1 in the semiconductor substrate 101. That is,the side surfaces of the second trench TR2 is formed so as to beperpendicularly extended below from the rear surface (upper surface) ofthe semiconductor substrate 101, and the side surfaces of the firsttrench TR1 is formed so as to be perpendicularly extended below from acenter portion of a bottom surface of the second trench TR2. Inaddition, the width of the second trench TR2 is formed so as to be widerthan that of the first trench TR1.

In addition, the trenches TR are formed so as to be symmetrical in adirection (a y direction (similar to an x direction)) along the rearsurface (upper surface) of the semiconductor substrate 101 between theplurality of pixels P.

Moreover, as illustrated in FIG. 3, the pixel separation portion 301includes a pinning layer 311, an insulating film 312, and a lightshielding layer 313, and each of the portions is provided in the innerportion of the trench TR.

As illustrated in FIG. 4, the planar shape of the pixel separationportion 301 is a lattice shape and interposed between the plurality ofpixels P. In addition, the trench TR is formed in a lattice shape in thepixel separation portion 301. Here, each of the first trench TR1 and thesecond trench TR2 is formed in a lattice shape. Moreover, the pinninglayer 311, the insulating film 312, and the light shielding layer 313are provided in the inner portion of the trench TR. In addition, thephotodiode 21 is formed in a rectangular region which is divided by thelattice shaped pixel separation portion 101 pb.

Each portion which configures the pixel separation portion 301 will bedescribed in detail.

(d-1) Pinning Layer 311

As illustrated in FIG. 3, the pinning layer 311 is provided in the innerportion of the first trench TR1 in the deeper portion of thesemiconductor substrate 101. Here, the pinning layer 311 is formed so asto bury the entire inner portion of the first trench TR1.

Moreover, the pinning layer 311 is formed so as to cover the surface ofthe inside of the second trench TR2 which is formed on the first trenchTR1 in the shallower portion of the semiconductor substrate 101. Here,the inner side surface of the pinning layer 311 is covered by theinsulating film 312 in the inner side portion of the second trench TR2.In addition, the inner side portion of the pinning layer 311, which iscovered by the insulating film 312, is embedded by the light shieldinglayer 313.

Moreover, the pinning layer 311 is formed so as to cover the lightsensing surface JS into which the incident light H enters on the rearsurface (upper surface) of the semiconductor substrate 101 in additionto the pixel separation portion 301.

Particularly, the pinning layer 311 is formed by using a high dielectricconstant material having a negative fixed charge so that a positivecharge (hole) accumulation region is formed and occurrence of a darkcurrent is suppressed in an interface portion between the pinning layerand the semiconductor substrate 101. Due to the fact that the pinninglayer 311 is formed so as to have the negative fixed charge, since anelectric field is added to the interface between the pinning layer andthe semiconductor substrate 101 by the negative fixed charge, thepositive charge (hole) accumulation region is formed.

In this way, the material of the pinning layer 311 has a higherdielectric constant than the material of the insulating film 312, andfor example, the pinning layer is formed by hafnium oxide (HfO₂).Besides this, the pinning layer 311 may be formed by zirconium dioxide(ZrO₂) or tantalum pentoxide (Ta₂O₅).

(d-2) Insulating Film 312

As illustrated in FIG. 3, the insulating film 312 is formed so as tocover the inside surface of the second trench TR2 which formed on thefirst trench TR 1 in the shallower portion of the semiconductorsubstrate 101.

Moreover, the insulating film 312 is formed so as to cover the lightsensing surface JS via the pinning layer 311 in the rear surface (uppersurface) of the semiconductor substrate 101 in addition to the pixelseparation portion 301 (refer to FIG. 4).

The insulating film 312 is formed by a material having a lowerdielectric constant than the pinning layer 311, for example, such asSiO₂.

(d-3) Light Shielding Layer 313

As illustrated in FIG. 3, the light shielding layer 313 is formed so asto bury the inner portion of the second trench TR2 via the pinning layer311 and the insulating film 312 in the shallower portion of thesemiconductor substrate 101.

Here, as illustrated in FIG. 4, the planar shape of the light shieldinglayer 313 is formed so as to be a lattice shape.

The light shielding layer 313 is formed by a light shielding materialwhich shields light. For example, the light shielding layer 313 isformed by using metal materials such as tungsten (W). The lightshielding layer 313 may be formed by using aluminum (Al) in addition tothe tungsten (W).

(e) Pixel Transistor Tr

In the solid-state imaging device 1, a plurality of pixel transistors Trare provided so as to correspond to the plurality of pixels Pillustrated in FIG. 2.

As illustrated in FIG. 5, the pixel transistor Tr includes a transfertransistor 22, an amplifying transistor 23, a selection transistor 24,and a reset transistor 25, reads the signal charge from the photodiode21, and outputs the read signal charge as an electric signal.

Although not illustrated in FIG. 3, each of the transistors 22 to 25which configure the pixel transistor Tr is provided on the front surfaceon which the wiring layer 111 is provided in the semiconductor substrate101. For example, each of the transistors 22 to 25 is an N channel MOStransistor, and for example, each gate is formed by using polysilicon.Moreover, each of the transistors 22 to 25 is covered by the wiringlayer 111.

In the pixel transistor Tr, as illustrated in FIG. 5, the transfertransistor 22 is configured so as to transfer the signal charge, whichis generated by the photodiode 21, to a floating diffusion FD.Specifically, as illustrated in FIG. 5, the transfer transistor 22 isprovided between a cathode of the photodiode 21 and the floatingdiffusion FD. In addition, the gate of the transfer transistor 22 iselectrically connected to the transfer line 26. The transfer transistor22 transfers the signal charge, which is accumulated in the photodiode21, to the floating diffusion FD based on a transfer signal TG which issent from the transfer line 26 to the gate.

In the pixel transistor Tr, as illustrated in FIG. 5, the amplifyingtransistor 23 is configured so as to amplify the electric signalconverted from the charge to the voltage in the floating diffusion FDand output the amplified electric signal. Specifically, as illustratedin FIG. 5, the gate of the amplifying transistor 23 is electricallyconnected to the floating diffusion FD. Moreover, the drain of theamplifying transistor 23 is electrically connected to a power supplyline Vdd, and the source of the amplifying transistor is electricallyconnected to the selection transistor 24. When the selection transistor24 is selected so as to be turned on, a constant current is supplied tothe amplifying transistor 23 from a constant current source I, and theamplifying transistor is operated as a source follower. Therefore, dueto the fact that the selection signal is supplied to the selectiontransistor 24, the electric signal, which is converted from the chargeto the voltage in the floating diffusion FD, is amplified in theamplifying transistor 23.

In the pixel transistor Tr, as illustrated in FIG. 5, the selectiontransistor 24 is configured so as to output the electric signal, whichis output by the amplifying transistor 23, to the vertical signal line27 based on the selection signal. Specifically, as illustrated in FIG.5, the gate of the selection transistor 24 is connected to an addressline 28 to which the selection signal is supplied. Moreover, theselection transistor 24 is turned on when the selection signal issupplied, and as described above, the selection transistor 24 outputsthe output signal, which is amplified by the amplifying transistor 23,to the vertical signal line 27.

In the pixel transistor Tr, as illustrated in FIG. 5, the resettransistor 25 is configured so as to reset the gate potential of theamplifying transistor 23. Specifically, as illustrated in FIG. 5, thegate of the reset transistor 25 is electrically connected to a resetline 29 to which the reset signal is supplied. Moreover, the drain ofthe reset transistor 25 is electrically connected to the power supplyline Vdd, and the source of the reset transistor is electricallyconnected to the floating diffusion FD. In addition, the resettransistor 25 resets the gate potential of the amplifying transistor 23to a power supply voltage via the floating diffusion FD based on thereset signal which is sent from the reset line 29.

FIG. 6 is a timing chart illustrating a control signal which is sent tothe pixel transistor Tr of the pixel P when imaging is performed in thefirst embodiment.

In FIG. 6, (a) illustrates a selection signal SEL which is input to thegate of the selection transistor 24. Moreover, (b) illustrates a resetsignal RST which is input to the gate of the reset transistor 25. Inaddition, (c) illustrates a transfer signal TG which is input to thegate of the transfer transistor 22 (refer to FIG. 5).

As illustrated in FIG. 6, when the imaging is performed, in a first timepoint t1, the selection transistor 24 is turned on while the selectionsignal SEL is set to a high level. Moreover, in a second time point t2,the reset transistor 25 is turned on while the reset signal RST is setto a high level. Thereby, the gate potential of the amplifyingtransistor 23 is reset (refer to FIG. 5).

In addition, as illustrated in FIG. 6, in a third time point t3, thereset transistor 25 is turned off while the reset signal RST is set to alow level. Moreover, thereafter, the voltage corresponding to the resetlevel is read to the column circuit 14 as an output signal (refer toFIGS. 2 and 5).

In addition, as illustrated in FIG. 6, in a fourth time point t4, thetransfer transistor 22 is turned on while the transfer signal TG is setto a high level. Thereby, the signal charge which is accumulated by thephotodiode 21 is transferred to the floating diffusion FD (refer to FIG.5).

In addition, as illustrated in FIG. 6, in a fifth time point t5, thetransfer transistor 22 is turned off while the transfer signal TG is setto a low level. Thereafter, the voltage of the signal levelcorresponding to the amount of the accumulated signal charge is read tothe column circuit 14 as an output signal (refer to FIGS. 2 and 5).

In the column circuit 14, a differential processing between the signalof the previously read reset level and the signal of the latterly readsignal level is preformed and the processed signal is accumulated (referto FIGS. 2 and 5).

Thereby, a fixed pattern noise, which is generated by variations or thelike of Vth in each transistor provided for each pixel P, is cancelledout.

Since each gate of the transistors 22, 24, and 25 is connected by a rowunit which includes a plurality of pixels P lined up in a horizontaldirection x, the operation driving the pixel P as described above issimultaneously performed with respect to the plurality of pixels P whichis lined up by the row unit.

Specifically, the pixels are sequentially selected in the perpendiculardirection by the horizontal line (pixel row) unit through the selectionsignal which is supplied by the above-described vertical drive circuit13. In addition, the transistors of each pixel P are controlled byvarious timing signals which are output from the timing generator 18.Therefore, the signals of each pixel are read to the column circuit 14for each column of the pixels P through the vertical signal line 27(refer to FIGS. 2 and 5).

Moreover, the signals accumulated by the column circuit 14 are selectedby the horizontal drive circuit 15 and sequentially output to theexternal output circuit 17 (refer to FIGS. 2 and 5).

In addition, the signal processing portion 44 performs the signalprocessing while having the signals obtained by the imaging as raw dataand generates a digital image (refer to FIG. 1).

(f) Wiring Layer 111

In the solid-state imaging device 1, as illustrated in FIG. 3, thewiring layer 111 is provided on the front surface (lower surface) of theside opposite to the rear surface (upper surface) on which each portionsuch as the color filter CF, and the microlens ML is provided in thesemiconductor substrate 101.

The wiring layer 111 includes wrings 111 h and the insulating layer 111z and is configured so that the wirings 111 h are electrically connectedto each element in the insulating layer 111 z. The wiring layer 111 is aso-called multilayer wiring and formed by laminating alternativelyinterlayer insulating films configuring the insulating layer 111 z andwirings 111 h a plurality of times. Here, the plurality of wirings 111 hare formed to be laminated via the insulating layer 111 z so as tofunction as each wiring of the transfer line 26, the address line 28,the vertical signal line 27, the reset line 29, or the like illustratedin FIG. 5.

Moreover, in the wiring layer 111, the supporting substrate SS isprovided on the surface of the side opposite to the side on which thesemiconductor substrate 101 is positioned. For example, a substratewhich includes a silicon semiconductor having a thickness of severalhundred μm is provided as the supporting substrate SS.

(B) Manufacturing Method

Main portions of a method for manufacturing the above-describedsolid-state imaging device 1 will be described.

FIGS. 7 to 13 are diagrams illustrating the method of manufacturing thesolid-state imaging device in the first embodiment of the presentdisclosure.

Similarly to FIG. 3, each of FIGS. 7 to 13 is illustrated in across-section.

In the present embodiment, the solid-state imaging device 1 illustratedin FIG. 3 or the like is manufactured sequentially through processesillustrated in each drawing.

The details of each process will be sequentially described.

(a) Formation of Photodiode 21 or the Like

First, as illustrated in FIG. 7, formation of the photodiode 21 or thelike is performed.

Here, each portion such as the photodiode 21 or the like is formed byion-implanting impurities from the front surface of the semiconductorsubstrate 101 including a single crystal silicon semiconductor. Forexample, after the p-type semiconductor region 101 pa is formed on theentire surface of the semiconductor substrate 101, the p-typesemiconductor region 101 pc having the higher impurity concentrationthan the p-type semiconductor region 101 pa is formed. Moreover, then-type semiconductor region 101 n is formed on the portion in which thephotodiode 21 is formed in the semiconductor substrate 101.

Moreover, after the pixel transistor Tr (not illustrated in FIG. 7) isformed on the front surface of the semiconductor substrate 101, thewiring layer 111 is formed so as to cover the pixel transistor Tr. Inaddition, the supporting substrate SS is bonded to the front surface ofthe wiring layer 111.

Thereafter, for example, the semiconductor substrate 101 is thinned. Forexample, the thinning may be performed according to the followingcondition.

-   -   Thickness of Semiconductor Substrate 101 after Thinning: 2.0 to        10 μm    -   Method: Chemical Mechanical Polishing (CMP) Method (In addition,        Dry Etching or Wet Etching is Possible)

Moreover, members such as the photodiode 21 and the pixel transistor Trare formed on a semiconductor layer of a SOI substrate (notillustrated), and similarly to the above-described one; after the wiringlayer 111 and the supporting substrate SS are provided, the thinningtreatment may be performed.

(b) Formation of Second Trench TR2

Next, as illustrated in FIG. 8, the second trench TR2 is formed.

Here, the second trench TR2 is formed in the pixel separation portion301 which is positioned between the plurality of pixels P in thesemiconductor substrate 101.

Specifically, as illustrated in FIG. 8, a hard mask HM is formed on therear surface (upper surface) of the semiconductor substrate 101 bypattern-processing. For example, the hard mask HM is formed by providinga thickness of a SiO₂ film such as HDP or P-TEOS so as to be 0.1 to 0.5μm.

For example, the hard mask HM is pattern-processed by performing the dryetching treatment of the following condition.

-   -   Chamber Pressure: 10 to 200 mTorr    -   Source Power: 500 to 3000 W (60 Hz)    -   Bias Power: 500 to 2000 W (2 MHz)    -   CF₄ Gas Flow: 10 to 200 sccm

Thereafter, the second trench TR2 is formed by processing thesemiconductor substrate 101 using the hard mask HM.

For example, the dry etching is performed to the silicon (Si)semiconductor substrate 101 and the second trench TR2 is formedaccording to the following condition.

-   -   Chamber Pressure: 5 to 100 mTorr    -   Source Power: 500 to 2000 W    -   Bias Power: 100 to 1000 W    -   Cl₂ Gas Flow: 10 to 300 sccm    -   O₂ Gas Flow: 1 to 50 sccm

For example, from the standpoint of a spectral characteristic, thesecond trench TR2 may be formed so as to satisfy the followingconditions.

-   -   Depth: 0.2 to 4 μm (preferably, 1.0 μm or more)    -   Width: 0.04 to 5 μm (the lower limit is preferable in order to        secure a refractive performance)

Moreover, in the present process, the hard mask HM may be formed by aSiN film such as P—SiN in addition to the above-described one.

(c) Formation of First Trench TR1

Next, as illustrated in FIG. 9, the first trench TR1 is formed.

Here, in the pixel separation portion 301 of the semiconductor substrate101, the first trench TR1 is formed on the bottom portion of the secondtrench TR2.

Specifically, as illustrated in FIG. 9, a side wall SW is formed at theopening portion of the hard mask HM and the inner surface of the secondtrench TR2. The side surface of the side wall SW is inclined so that theopening of the hard mask HM and the width of the second trench TR2 arenarrowed toward the lower portion of the semiconductor substrate 101.For example, the side wall SW is formed by forming different kind offilms such as P—SiN and performing of a dry etching with respect to thefilms.

Moreover, the first trench TR1 is formed by processing the semiconductorsubstrate 101 using the hard mask HM, on which the side wall SW isprovided, as the mask.

For example, in order to perform the dry etching processing of thesemiconductor substrate 101, the first trench TR1 may be formedaccording to the following condition.

-   -   Depth: 0.3 to 10 μm (it is preferable that the depth is 1.5 μm        or more from the rear surface (upper surface) of the        semiconductor substrate 101 and from a blooming characteristic)    -   Width: 0.02 to 5 μm or more (in order to secure an insulation        performance, the lower limit is preferable and 0.05 μm or more        is further preferable)    -   (d) Removal of Hard Mask HM and Side Wall SW

Next, as illustrated in FIG. 10, the hard mask HM and the side wall SWare removed.

Here, for example, the hard mask HM and the side wall SW are removedfrom the rear surface (upper surface) of the semiconductor substrate 101by performing an etching processing to the hard mask HM and the sidewall SW. Thereby, the rear surface (upper surface) of the semiconductorsubstrate 101 is exposed.

(e) Formation of Pinning Layer 311

Next, as illustrated in FIG. 11, the pinning layer 311 is formed.

Here, the pinning layer 311 is formed so as to bury the entire innerportion of the first trench TR1 in the deeper portion of thesemiconductor substrate 101.

Moreover, the pinning layer 311 is formed so as to cover the insidesurface of the second trench TR2, which is formed on the first trenchTR1, in the shallower portion of the semiconductor substrate 101.

In addition, the pinning layer 311 is formed so as to cover the lightsensing surface JS into which the incident light H enters on the rearsurface (upper surface) of the semiconductor substrate 101 in additionto the pixel separation portion 301.

The material of the pinning layer 311 is an insulation material whichhas a higher dielectric constant than that of the insulating film 312,and uses a high dielectric constant material having a negative fixedcharge.

For example, the pinning layer 311 is formed according to the followingcondition.

-   -   Material: HfO₂    -   Formation Method: Chemical Vapor Deposition (CVD) Method    -   Thicknesses of Inside Surface of Second Trench TR2 and Upper        Portion of Semiconductor Substrate 101: 1 to 200 nm

For example, the pinning layer 311 may be formed also by using amaterial such as Al₂O₃, ZrO₂, TiO₂, Ta₂O₅, or MgO₂ in addition to HfO₂.The materials are proven to be useful in a gate insulating film of aninsulating gate-type electric field effect transistor or the like.Therefore, the pinning layer is easily formed since the film formingmethod is established.

Among the materials, it is more preferable to use the hafnium oxide(HfO₂), the tantalum pentoxide (Ta₂O₅), and the aluminum oxide (Al₂O₃).Since the material has a high pinning performance (negative fixed chargeamount), suppression effects to a white point and a dark current can bepreferably obtained. Moreover, the materials are preferable since a highprocess practicability can be obtained.

Besides this, materials such as lanthanum oxide (La₂O₃), praseodymiumoxide (Pr₂O₃), cerium oxide (CeO₂), neodymium oxide (Nd₂O₃), promethiumoxide (Pm₂O₃), samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃),gadolinium oxide (Gd₂O₃), terbium oxide (Tb₂O₃), dysprosium oxide(Dy₂O₃), holmium oxide (Ho₂O₃), erbium oxide (Er₂O₃), thulium oxide(Tm₂O₃), ytterbium oxide (Yb₂O₃), lutetium oxide (Lu₂O₃), yttrium oxide(Y₂O₃) can be used. Moreover, the pinning layer 311 can be used by usinga hafnium nitride film, an aluminum nitride film, a hafnium oxynitridefilm, or an aluminum oxynitride film.

In addition, the pinning layer 311 may be formed according to variousfilm forming methods such as a sputtering method or Atomic LayerDeposition (ALD) method in addition to the Chemical Vapor Deposition(CVD) method.

For example, when the hafnium oxide (HfO₂) film is formed according toan Organic Metal Chemical Vapor Deposition method (MOCVD method), thefilm formation is performed according to the following manufacturingcondition by using the following precursor.

-   -   Precursor: TEMA-Hf (Tetrakis ethylmethylamido hafnium), TDMA-Hf        (Tetrakis dimethylamido hafnium), or TDEA-Hf (Tetrakis        diethylamido hafnium)    -   Film Formation Substrate Temperature: 200° C. to 600° C.    -   Flow Rate of Precursor: 10 cm³/min to 500 cm³/min    -   Illumination Time of Precursor: 1 to 15 seconds    -   Flow Rate of Ozone (O₃): 5 cm³/min to 50 cm³/min

In addition, when the hafnium oxide film is formed according to theAtomic Layer Deposition method (ALD method), the film formation isperformed according to the following manufacturing condition by usingthe following precursor.

-   -   Precursor: TEMA-Hf (Tetrakis ethylmethylamido hafnium), TDMA-Hf        (Tetrakis dimethylamido hafnium), or TDEA-Hf (Tetrakis        diethylamido hafnium)    -   Film Formation Substrate Temperature: 200° C. to 500° C.    -   Flow Rate of Precursor: 10 cm³/min to 500 cm³/min    -   Illumination Time of Precursor: 1 to 15 seconds    -   Flow Rate of Ozone (O₃): 5 cm³/min to 50 cm³/min

Since SiO₂ layer decreasing the interface potential during the filmformation can be simultaneously formed to about 1 nm in the Atomic LayerDeposition method, the ALD method is more preferable.

Besides this, an antireflective film may be formed on the pinning layer311.

(f) Formation of Insulating Film 312

Next, as illustrated in FIG. 12, the insulating film 312 is formed.

Here, the insulating film 312 is formed so as to cover the insidesurface of the second trench TR2 which is formed on the first trench TR1in the shallower portion of the semiconductor substrate 101.

Moreover, the insulating film 312 is formed on the rear surface (uppersurface) of the semiconductor substrate 101 in addition to the pixelseparation portion 301 so that the insulating film 312 covers the lightsensing surface JS via the pinning layer 311.

The insulating film 312 is formed by using a material having a lowerdielectric constant than the material of the pinning layer 311.

For example, the insulating film 312 may be formed according to thefollowing condition.

-   -   Material: SiO₂    -   Formation Method: CVD method    -   Thickness: 5 μm or less (in order to secure sensitivity)

(g) Formation of Light Shielding Layer 313

Next, as illustrated in FIG. 13, the light shielding layer 313 isformed.

Here, the light shielding layer 313 is formed so as to bury the innerportion of the second trench TR2 via the pinning layer 311 and theinsulating film 312 in the shallower portion of the semiconductorsubstrate 101.

The light shielding layer 313 is formed by using a light shieldingmaterial which shields light.

For example, the light shielding layer 313 may be used according to thefollowing condition.

-   -   Material: Tungsten (W)    -   Formation Method: Sputtering Method

In the present process, the light shielding layer 313 is formed on therear surface (upper surface) of the semiconductor substrate 101 so as tobury the inner portion of the second trench TR2. Thereafter, in thelight shielding layer 313, the portion which is provided on the rearsurface (upper surface) of the semiconductor substrate 101 is removed.Thereby, the light shielding layer 313 is not formed on the lightsensing surface JS and is embedded to the inner portion of the secondtrench TR2. Therefore, the pixel separation portion 301 is formedbetween the plurality of pixels P.

In addition, the light shielding layer 313 may be formed by forming thefilm of other light shielding materials through other film formingmethods such as the CVD method.

The light shielding layer 313 may be formed by using aluminum (Al) inaddition to the tungsten (W). When metals (for example, copper) otherthan aluminum or tungsten are used, a reflective performance may bedecreased in a portion of a visual light range. In addition, when ametal having a high diffusion coefficient in silicon other than aluminumor tungsten is used, since the metal may be diffused into the siliconsemiconductor substrate 101, occurrence of a dark current may beincreased.

(h) Formation of Color Filter CF and Microlens ML

Next, as illustrated in FIG. 3, each member of the color filter CF andthe microlens ML is formed.

Here, the color filter CF is formed on the rear surface (upper surface)of the semiconductor substrate 101.

For example, the color filter CF is formed by pattern-processing acoating film through a lithography technology after applying anapplication liquid including coloring matters such as pigments or dyesand photosensitive resins through a coating method such as thespin-coating method and forming the coating film. Thereby, the colorfilter CF is provided by forming each of the filter layers CFR, CFG, andCFB.

Thereafter, the microlens ML is provided on the upper surface of thecolor filter CF.

For example, after a photosensitive resin film is pattern-processedthrough a photolithography technology, the microlens ML is formed bydeforming the pattern-processed resin into a lens shape through a reflowtreatment. Beside this, after a resist pattern of a lens shape is formedon a lens material film, the microlens ML may be formed by performing anetch-back processing while having the resist pattern as a mask.

In this way, the “rear surface illumination type” of CMOS image sensoris completed by performing sequentially each process.

(C) Conclusion

As described above, in the present embodiment, the plurality ofphotodiodes 21 which receive the incident light H through the lightsensing surface JS are provided so as to correspond to the plurality ofpixels P in the inner portion of the semiconductor substrate 101respectively. Moreover, the pixel separation portion 301 is provided inthe inner portion of the semiconductor substrate 101 between theplurality of pixels P (refer to FIG. 3).

As described above, unlike the present embodiment, when the pixelseparation portion 101 pb is formed by ion-implanting an impurity havinga high concentration from the front surface (lower surface) side of thesemiconductor substrate 101 (refer to FIG. 23), the image quality may bedecreased because of occurrence of the optical noise due to leakage ofthe inclined light. For example, a “color mixing” is generated, andcolor reproducibility in the captured color image may be decreased. Inaddition, quality of the captured image may be decreased due tooccurrence of “shading”.

Besides this, when the pixel separation portion 101 pb (refer to FIG.23) is formed by ion-implanting an impurity having a high concentration,the width of the pixel separation portion 101 pb is widened withconsideration for diffusion of the impurity or the like. Particularly,in the case of the “rear surface illumination type”, the width of thepixel separation portion 101 pb is widened in the rear surface (uppersurface) side of the semiconductor substrate 101. Thereby, it may bedifficult to widen the occupancy area of the photodiode 21. Therefore, asaturation charge accumulation amount (Qs) of the photodiode 21 isdecreased, and it may be difficult to improve the quality of thecaptured image.

Moreover, since light having a shorter wavelength is absorbed in thevicinity of the rear surface (upper surface) into which the light entersin the semiconductor substrate 101 which is formed of a single crystalsilicon semiconductor, particularly, the “color mixing” may besignificantly generated between pixels which receive the light havingthe shorter wavelength such as blue.

However, in the present embodiment, the pinning layer 311, theinsulating layer 312, and the light shielding layer 313 are embeddedinto the trench TR which is provided at the side portion of thephotodiode 21 in the rear surface (incident surface) side into which theincident light H enters in the semiconductor substrate 101 (refer toFIG. 3). Thereby, the pixel separation portion 301 shields light andoptically separates the plurality of pixels P, and insulates andelectrically separates the plurality of pixels P. Therefore, since bothfunctions of the light shielding between pixels and the elementseparation are realized in the pixel separation portion 301, it ispossible to improve a spectral characteristic and a bloomingcharacteristic in the present embodiment.

Moreover, since the pixel separation portion 301 is not formed byion-implanting an impurity having a high concentration in the presentembodiment, the saturation charge accumulation amount (Qs) is notdecreased, and it is possible to easily improve quality of the capturedimage.

Besides this, in the present embodiment, the trench TR of a multistagestructure including the first trench TR1 and the second trench TR2 isprovided in the pixel separation portion 301. Here, the width of thesecond trench TR2 is formed so as to be wider than the width of thefirst trench TR1 in the portion shallower than the first trench TR 1 inthe semiconductor substrate 101.

Moreover, in the present embodiment, the pinning layer 311 is formed soas to bury the inner portion of the first trench TR1 and cover theinside surface of the second trench TR2. In addition, the insulatingfilm 312 is formed so as to cover the inside surface of the secondtrench TR2 via the pinning layer 311. Moreover, the light shieldinglayer 313 is formed so as to bury the inner portion of the second trenchTR2 via the pining layer 311 and the insulating film 312.

In this way, in the present embodiment, since the pixel separationportion 301 includes the pinning layer 311, occurrence of a dark currentis suppressed, and occurrence of a white point in the captured image canbe prevented. Moreover, since the pinning layer 311 includes thenegative fixed charge, carriers (electrons or holes) generated whenforming the trench in the rear surface can be held to the fixed charges.

Moreover, in the trench TR of the multistage structure of the presentembodiment, the metal material is not embedded to the first trench TR1of the deeper position, the metal material is embedded to the innerportion of the second trench TR2 which is provided on the shallowposition of the uppermost stage, and the light shielding layer 313 isformed. Thereby, the light shielding layer 313 can be formed byuniformly burying the metal material to the second trench TR2 withoutvoids. Therefore, since the light shielding layer 313 can effectivelyshield light between the plurality of pixels P, occurrence of the “colormixing” and occurrence of the “shading” can be prevented. That is, whenthe metal material is embedded into the deeper trench (for example, thedepth is 0.5 μm or more) as the light shielding material, voids aregenerated and it is difficult to uniformly bury the metal material.Therefore, it is difficult to prevent the “color mixing” and the“shading” from being generated. However, the disadvantageous can besolved according to the present embodiment.

Therefore, it is possible to improve quality of the captured image inthe present embodiment.

2. Second Embodiment

(A) Manufacturing Method

FIGS. 14 and 15 are diagrams illustrating the method of manufacturing asolid-state imaging device in a second embodiment.

Similarly to FIG. 3, each of FIGS. 14 and 15 is illustrated in across-section.

In the manufacturing of the solid-state imaging device of the presentembodiment, similarly to the case of the first embodiment, the formationof the photodiode 21 or the like (refer to FIG. 7) and the formation ofthe second trench TR2 (refer to FIG. 8) are performed. Thereafter, thefirst trench TR1 is formed sequentially through processes illustrated inFIGS. 14 and 15. In addition, similarly to the case of the firstembodiment, the formation of the pinning layer 311 (refer to FIG. 11),the formation of the insulating film 312 (refer to FIG. 12), theformation of the light shielding layer 313 (refer to FIG. 13), theformation of the color filter CF, and the formation of the microlens ML(refer to FIG. 3) are performed.

As illustrated in FIGS. 14 and 15, in the present embodiment, theprocess for forming the first trench TR1 is different from that of thefirst embodiment. Except for this point and those related to the point,the present embodiment is similar to the first embodiment. Thereby,description is appropriately omitted with respect to the overlappedportions.

The detail of each process will be sequentially described like thefollowing.

(a) Formation of Photoresist Pattern PR

After the second trench TR2 is formed (refer to FIG. 8), the photoresistpattern PR is formed as illustrated in FIG. 14.

Here, after a photoresist film (not illustrated) is formed on the rearsurface (upper surface) of the semiconductor substrate 101 on which thehard mask HM is formed, the photoresist pattern PR is formed bypattern-processing the photoresist film (not illustrated) through alithography technology.

Specifically, in the rear surface (upper surface) side of thesemiconductor substrate 101, the pattern shape of the photoresistpattern PR is formed so that the portion on which the first trench TR1is formed is opened and other portions are covered. That is, thephotoresist pattern PR is formed so as to be the state where theportion, in which the first trench TR1 is formed on the bottom surfaceof the second trench TR2, is exposed and the other inner surfaces of thesecond trench TR2 are covered.

(b) Formation of First Trench TR1

Next, as illustrated in FIG. 15, the first trench TR1 is formed.

Here, similarly to the case of the first embodiment, the first trenchTR1 is formed on the bottom portion of the second trench TR2 in thepixel separation portion 301 of the semiconductor substrate 101.

Moreover, the rear surface is exposed by removing the photoresistpattern PR and the hard mask HM from the rear surface (upper surface)side of the semiconductor substrate 101.

Thereafter, similarly to the case of the first embodiment, the “rearsurface illumination type” CMOS image sensor is completed through eachprocess.

(B) Conclusion

As described above, the solid-state image device having the sameconfiguration as that of the case of the first embodiment can be formedin the present embodiment.

Therefore, the same effects as those of the case of the first embodimentcan be preferably achieved in the present embodiment.

3. Third Embodiment

(A) Device Configuration

FIG. 16 is a diagram illustrating main portions of a solid-state imagingdevice in a third embodiment.

FIG. 16 illustrates the cross-section of the pixel P similarly to FIG.3.

As illustrated in FIG. 16, in the present embodiment, the pinning layer311 c and the insulating film 312 c are different from the firstembodiment. Except for this point and those related to the point, thepresent embodiment is similar to the first embodiment. Thereby,description is appropriately omitted with respect to the overlappedportions.

(a) Pinning Layer 311 c

As illustrated in FIG. 16, similarly to the case of the firstembodiment, the pinning layer 311 c is formed so as to cover the insidesurface of the second trench TR2 which is formed on the first trench TR1in the shallower portion of the semiconductor substrate 101.

However, as illustrated in FIG. 16, unlike the case of the firstembodiment, the pinning layer 311 c is not formed so as to bury theentire inner portion of the first trench TR1 in the deeper portion ofthe semiconductor substrate 101.

Here, the pinning layer 311 c is formed so as to cover the insidesurface of the first trench TR1.

(b) Insulating Film 312 c

As illustrated in FIG. 16, similarly to the case of the firstembodiment, the insulating film 312 c is formed so as to cover theinside surface of the second trench TR2, which is formed on the firsttrench TR1 in the shallower portion of the semiconductor substrate 101,via the pinning layer 311 c.

However, as illustrated in FIG. 16, unlike the case of the firstembodiment, the insulating film 312 c is also formed at the innerportion of the first trench TR1 in the deeper portion of thesemiconductor substrate 101.

Here, the insulating film 312 c is formed so as bury the inner portionof the first trench TR1 via the pinning layer 311 c.

(B) Manufacturing Method

The main portions of the method for manufacturing the solid-stateimaging device will be described.

FIGS. 17 and 18 are diagrams illustrating the method of manufacturingthe solid-state imaging device in the third embodiment.

Similarly to FIG. 16, each of FIGS. 17 and 18 is illustrated in across-section.

In the manufacturing of the solid-state imaging device of the presentembodiment, similarly to the case of the first embodiment, the formationof the photodiode 21 or the like, the formation of the second trenchTR2, the formation of the first trench TR1, the removal of the hard maskHM and the side wall SW are performed (refer to FIGS. 7 to 10).Thereafter, the solid-state imaging device illustrated in FIG. 16 or thelike is formed sequentially through processes illustrated in FIGS. 17and 18.

Moreover, after the formation of the first trench TR1 is performedthrough the similar processes as those of the case of the secondembodiment, the solid-state imaging device illustrated in FIG. 16 or thelike may be formed sequentially through the processes illustrated inFIGS. 17 and 18.

The detail of each process will be sequentially described like thefollowing.

(a) Formation of Pinning Layer 311 c and Insulating Layer 312 c

As described above, after the first trench TR1, the second trench TR2,and the like are formed, the pinning layer 311 c and the insulatinglayer 312 c are formed as illustrated in FIG. 17.

Here, the pinning layer 311 c is formed so as to cover the insidesurface of each of the first trench TR1 and the second trench TR2.

For example, similarly to the case of the first embodiment, the pinninglayer 311 c is formed by forming the HfO₂ film.

Thereafter, the insulating film 312 c is formed so as to bury the innerside portion of the first trench TR1 which is covered by the pinninglayer 311 c and cover the inside surface of the second trench TR2.

For example, similarly to the case of the first embodiment, theinsulating film 312 c is formed by forming the SiO₂ film.

(b) Formation of Light Shielding Layer 313

Next, the light shielding layer 313 is formed as illustrated in FIG. 18.

Here, similarly to the case of the first embodiment, the light shieldinglayer 313 is formed so as to bury the inner portion of the second trenchTR2 via the pinning layer 311 c and the insulating film 312 c.

(C) Formation of Color Filter CF and Microlens ML

Next, as illustrated in FIG. 16, each member such as the color filter CFand the microlens ML is formed similarly to the case of the firstembodiment.

Thereby, the “rear surface illumination type” CMOS image sensor iscompleted.

(c) Conclusion

As described above, similarly to the case of the first embodiment, inthe present embodiment, the pinning layer 311 c is formed in the innerportion of the first trench TR1 so as to cover the inside surface of thesecond trench TR2. The insulating film 312 c is formed so as to coverthe inside surface of the second trench TR2 via the pinning layer 311 c.In addition, the light shielding layer 313 is formed so as to bury theinner portion of the second trench TR2 via the pinning layer 311 c andthe insulating film 312 c.

Here, the pinning layer 311 c is formed so as to cover the insidesurface of the first trench TR1. Moreover, the insulating film 312 c isformed so as to bury the inner portion of the first trench TR1 via thepinning layer 311 c.

Therefore, similarly to the case of the first embodiment, it is possibleto improve quality of the captured image in the present embodiment.

Moreover, the insulating film 312 c has the effect compensating apinning property. Thereby, due to the fact that the insulating film 312c is provided in the first trench TR1, a stronger pinning property canbe realized.

4. Fourth Embodiment

(A) Device Configuration or the Like

FIGS. 19 to 21 are diagrams illustrating main portions of a solid-stateimaging device in a fourth embodiment.

Similarly to FIG. 16, FIGS. 19 and 20 are the cross-sectional diagramsof the pixel P. In addition, FIG. 21 is a top view of the pixel P.

Here, FIG. 19 is a cross-sectional diagram taken along a line XIX-XIXillustrated in FIG. 21, and illustrates the cross-section of the pixel Pon which the red filter layer CFR is provided in the plurality of pixelsP. Other than this, the pixel separation portion 301, which ispositioned at the periphery of the pixel P on which the red filter layerCFR is provided, is formed similarly to the case of FIG. 21.

Moreover, FIG. 20 is a cross-sectional diagram taken along a line XX-XXillustrated in FIG. 21, and illustrates the cross-section of the pixel Pon which the blue filter layer CFB is provided in the plurality ofpixels P. Other than this, in the pixel separation portion 301, portionsother than the portion, which is positioned in the periphery of thepixel P on which the red filter layer CFR is provided, are formedsimilarly to the case of FIG. 21.

Moreover, in FIG. 21 similarly to FIG. 4, for convenience ofdescription, in some cases, portions which illustrate each member aredenoted by a broken line or the like other than a solid line.

As illustrated in each of FIGS. 19 to 20, in the present embodiment, inthe pixel separation portion 301, the portion which is positioned in theperiphery of the pixel P on which the red filter layer CFR is providedand portions other than the portion are different from each other. Thatis, in other embodiments, the pixel separation portion 301 is formed inthe same shape between each pixel P. However, in the present embodiment,the shape of the pixel separation portion 301 is changed according tothe wavelength range of the received light in each pixel P. Except forthis point and those related to the point, the present embodiment issimilar to the first embodiment. Thereby, description is appropriatelyomitted with respect to the overlapped portions.

In the present embodiment, as illustrated in FIGS. 19 and 20, in thetrench TR, the peripheral portion of the photodiode 21 of the pixel Pfor which the red light is transmitted by the red filter layer CFR isformed up to a deeper portion than the portions between the pixels Pwhich receive other green and blue light. That is, the trench TR in theportion of the periphery of the pixel P, in which the filter layer CFRhaving higher transmissivity with respect to the wavelength range of thelongest wavelength in the plurality of kinds of filter layers CFR, CFG,and CFB is disposed, among the plurality of pixels P is deeper than thetrench in the portion of other pixels P.

Here, the first trench TR1 d (FIG. 19) of the peripheral portion of thepixel P, which receives the red light having the wavelength range of thelongest wavelength among the plurality of pixels P, is formed so as tobe deeper than the first trench TR1 (FIG. 20) of the other portions.

For example, the depths of the first trenches TR1 and TR1 d from therear surface (upper surface) of the semiconductor substrate 101 may beformed so as to satisfy the following conditions. By this way, ablooming characteristic can be preferably obtained.

-   -   The portion which is positioned in the periphery of the pixel P        on which the red filter layer CFR is provided: 0.2 μm or more        (preferably, 1.5 μm or more)    -   Portions other than the above portion: 0.2 μm or more        (preferably, 1.0 μm or more)

Moreover, the pinning layer 311 d is formed so as to cover the insidesurface of the first trench TR1 and TR1 d. In addition, the insulatingfilm 312 d is formed so as to bury the inner portion of the first trenchTR1 via the pinning layer 311 c.

(B) Conclusion

As described above, similarly to the third embodiment, in the presentembodiment, the pinning layer 311 d is formed in the inner portion ofthe first trench TR1 so as to cover the inside surface of the secondtrench TR2. The insulating film 312 d is formed so as to cover theinside surface of the second trench TR2 via the pinning layer 311 d. Inaddition, the light shielding layer 313 is formed so as to bury theinner portion of the second trench TR2 via the pinning layer 311 d andthe insulating film 312 d.

Therefore, similarly to the case of the third embodiment, in the presentembodiment, it is possible to improve quality of the captured image.

Moreover, in the present embodiment, the trench TR in the portion of theperiphery of the pixel P, in which the filter layer CFR having highertransmissivity with respect to the wavelength range of the longestwavelength in the plurality of kinds of filter layers CFR, CFG, and CFBis disposed, is deeper than the trench in the portion of other pixels P.In addition, the pinning layer 311 d, the insulating film 312 d, and thelight shielding layer 313 are provided in the trench TR.

In the semiconductor substrate 101 which is formed of a single crystalsilicon semiconductor, the light of the shorter wavelength like the bluelight is absorbed in the vicinity of the surface into which the lightenters. However, the light having the longer wavelength like the redlight reaches the deeper portion of the semiconductor substrate 101. Incontrast, in the present embodiment, the pinning layer 311 d and theinsulating film 312 d in the periphery of the photodiode 21 whichreceives the light having the longer wavelength like the red light areformed up to a deeper position than the periphery of the photodiode 21which receives other light having the shorter wavelength.

Thereby, in the present embodiment, even when the light having thelonger wavelength reaches the deeper portion of the semiconductorsubstrate 101 and an electric charge is generated, the pixel separationportion 301 can electrically separate between the plurality of pixels Pwith effect.

In addition, the trench TR is formed so as to be shallower in theportions other than the portion of the periphery of the pixel P, inwhich the filter layer CFR having higher transmissivity with respect tothe light of the wavelength range of the longest wavelength ispositioned, among the plurality of pixels P. In the case where a deeptrench TR is formed, damage due to the etching processing or the likemay be great. However, the damage can be decreased in the shallowerportion.

Therefore, in the present embodiment, it is possible to further improvequality of the captured image.

In addition, in the above-described embodiment, similarly to the case ofthe third embodiment, the case where the pinning layer 311 d and theinsulating film 312 d are provided in the inner portion of the firsttrenches TR1 and TR1 d is described. However, the present disclosure isnot limited thereto. That is, similarly to the cases of the first andsecond embodiments, only the pinning layer 311 may be provided in theinner portion of the first trenches TR1 and TR1 d.

In addition, in the present embodiment, unlike the first trenches TR1and TR1 d of the lower stage which are different from each other, theperipheral portion of the pixel P which receives the red light and otherportions have the same depth as each other in the second trench TR2 ofthe upper stage. However, the present disclosure is not limited thereto.Similarly to the first trenches TR1 and TR1 d of the lower stage, alsoin the second trenches TR2 of the upper stage, the peripheral portion ofthe pixel P which receives the red light may be formed so as to bedeeper than other portions.

For example, the depth of the second trench TR2 from the rear surface(upper surface) of the semiconductor substrate 101 may be formed so asto be the following condition.

-   -   The portion which is positioned in the periphery of the pixel P        on which the red filter layer CFR is provided: 0.2 to 4 μm        (preferably, 1.0 μm or more)    -   Portions other than the above portion: 0.2 to 4 μm or more        (preferably, 0.5 μm or more)

5. Fifth Embodiment

(A) Device Configuration or the Like

FIG. 22 is a diagram illustrating main portions of a solid-state imagingdevice in a fifth embodiment.

FIG. 22 illustrates the cross-section of the pixel P similarly to FIG.3.

As illustrated in FIG. 22, the solid-state imaging device of the presentembodiment is a “front surface illumination type”. That is, the wiringlayer 111 is provided on the front surface (upper surface in FIG. 22)side of the semiconductor substrate 101, and the light sensing surfaceJS receives the incident light H which enters from the front surfaceside. Moreover, the pixel separation 301 is provided on the frontsurface (upper surface) side of the semiconductor substrate 101. Inaddition, the semiconductor substrate 101 is not thinned, and thesupporting substrate SS (refer to FIG. 3) is not provided. Except forthis point and those related to the point, the present embodiment issimilar to the first embodiment. Thereby, description is appropriatelyomitted with respect to the overlapped portions.

In the present embodiment, as illustrated in FIG. 22, in the solid-stateimaging device, the photodiode 21 and the pixel separation portion 301are provided in the inner portion of the semiconductor substrate 101.

As illustrated in FIG. 22, the photodiode 21 is provided so that then-type semiconductor region 101 n is positioned in the inner portion ofthe p-type semiconductor regions 101 pa and 101 pc at the front surface(upper surface) side of the semiconductor substrate 101.

As illustrated in FIG. 22, the pixel separation portion 301 isconfigured similarly to the first embodiment. That is, the pixelseparation 301 includes the pinning layer 311, the insulating film 312,and the light shielding layer 313, and each of the portions is providedin the inner portion of the trench TR.

In the wiring layer 111, the wirings 111 h are provided on a portionother than the upper portion of the light sensing surface JS in theinsulating layer 111 z.

Moreover, similarly to the first embodiment, the color filter CF and themicrolens ML are provided on the upper surface of the wiring layer 111.

Although not illustrated in FIG. 22, the pixel transistor Tr illustratedin FIG. 5 is provided on the front surface (upper surface) of thesemiconductor substrate 101. The wiring layer 111 is provided so as tocover the pixel transistor Tr.

In the present embodiment, similarly to the first embodiment, when theimage device is manufactured, the p-type semiconductor region 101 pa,the p-type semiconductor region 101 pc, and the n-type semiconductorregion 101 n are formed by ion-implanting impurities from the frontsurface of the semiconductor substrate 101. Moreover, similarly to thefirst embodiment, the trench TR is formed on the front surface side ofthe semiconductor substrate 101. In addition, similarly to the firstembodiment, the pinning layer 311, the insulating film 312, and thelight shielding layer 313 are formed in the trench TR. Moreover, afterthe pixel transistor Tr is formed on the front surface of thesemiconductor substrate 101, the wiring layer 111 is formed so as tocover the pixel transistor Tr. In addition, the color filter CF and themicrolens ML are formed, and the “front surface illumination type” CMOSimage sensor is completed.

(B) Conclusion

As described above, in the present embodiment, similarly to the case ofthe first embodiment, the pixel separation portion 301 includes thepinning layer 311, the insulating film 312, and the light shieldinglayer 313, and each of the portions is provided in the inner portion ofthe trench TR (refer to FIG. 22).

Therefore, similarly to the first embodiment, it is possible to improvequality of the captured image in the present embodiment.

As described above, the solid-state imaging device of the presentembodiment is the “front surface illumination type”. In the case of the“front surface illumination type”, when the pixel separation portion isprovided by ion-implanting impurities having a high concentration fromthe front surface side into which the incident light enters,particularly, it is difficult to improve the saturation chargeaccumulation amount (Qs) of the pixel which receives the light havingthe longer wavelength like the red. The reason is that the width of thepixel separation portion, which becomes the impurity region having ahigh concentration in the rear surface (lower surface) side of thesemiconductor substrate 101, is easily widened considering the diffusionof impurities.

However, in the present embodiment, the pixel separation portion 301 isembedded to the inner portion of the trench TR provided in the sideportion of the photodiode 21 in the semiconductor substrate 101.Thereby, since the pixel P is separated in the deeper region withrespect to the light sensing surface JS, particularly, it is possible toincrease the saturation charge accumulation amount (Qs) in thephotodiode 21 which receives the red light, and a dynamic range can beimproved.

Moreover, in the present embodiment, the case where the pixel separationportion 301 is configured so as to be the same as the case of the firstembodiment is described. However, the present disclosure is not limitedthereto, and the pixel separation portion 301 may be configured like theother embodiments.

6. Others

When the present disclosure is performed, the present disclosure is notlimited to the above-described embodiments. That is, the presentdisclosure can adopt various modifications.

In the above-described embodiments, the case where the presentdisclosure is applied to the camera is described. However, the presentdisclosure is not limited thereto. That is, the present disclosure maybe also applied to other electronic apparatuses including a solid-stateimaging device such as a scanner or a copier.

In the above-described embodiments, the case where four kinds of thetransfer transistor, the amplifying transistor, the selectiontransistor, and the reset transistor are provided as the pixeltransistor is described. However, the present disclosure is not limitedthereto. For example, the present disclosure may be also applied to acase where three kinds of the transfer transistor, the amplifyingtransistor, and the reset transistor are provided as the pixeltransistor.

In the above-described embodiments, the case where each of the transfertransistor, the amplifying transistor, the selection transistor, and thereset transistor is provided to one photodiode one by one is described.However, the present disclosure is not limited thereto. For example, thepresent disclosure may be also applied to a case where each of theamplifying transistor, the selection transistor, and the resettransistor is provided to a plurality of photodiodes one by one.

Moreover, the present disclosure may be applied to a CCD type imagesensor in addition to the CMOS type image sensor.

Moreover, in the above described embodiment, the case where the pixelseparation portion 301 includes the insulating film 312 is described.However, the present disclosure is not limited thereto. The insulatingfilm 312 may not provided.

Moreover, in the manufacturing of the solid-state imaging device, whenthe trench TR is formed in the portion which forms the pixel separationportion 301, the trench may be simultaneously formed with respect toother portions. For example, when the surface of a pad electrode (notillustrated) formed similarly to the wirings 111 h is exposed in thewiring layer 111, the trench may be formed on the upper portion of thesurface in the same process as the above one. By this way, it ispossible to further improve the producibility.

Moreover, in the above, the case where the trench TR includes atwo-stage structure is described. However, the present disclosure is notlimited thereto. The trench TR including the stages having three or moremay be configured. In this case, for example, the pixel separationportion is provided by embedding the light shielding layer into theuppermost stage and the pinning layer or the insulating film into thestates other than the uppermost stage.

In addition, the above-described embodiments may be appropriatelycombined.

That is, the present disclosure may include the followingconfigurations.

(1) According to an embodiment of the present disclosure, there isprovided a solid-state imaging device including a plurality ofphotoelectric conversion portions each provided to correspond to each ofa plurality of pixels in a semiconductor substrate and receives incidentlight through a light sensing surface, and a pixel separation portionthat is provided between the plurality of pixels in an inner portion ofthe semiconductor substrate and electrically separates the plurality ofpixels, wherein at least a pinning layer and a light shielding layerthat are provided in an inner portion of a trench which is provided on aside portion of each of the photoelectric conversion portions in anincident surface side of the semiconductor substrate into which theincident light enters, the trench includes a first trench and a secondtrench having a width wider than that of the first trench in a portionshallower than the first trench in the semiconductor substrate, thepinning layer is formed in an inner portion of the first trench so as tocover an inside surface of the second trench, and the light shieldinglayer is formed so as to bury an inner portion of the second trench atleast via the pinning layer.

(2) In the solid-state imaging device described in (1), the pinninglayer may be formed so as to bury the entire inner portion of the firsttrench.

(3) In the solid-state imaging device described in (2), the solid-stateimaging device may further include an insulating film that is formed soas to cover the inside surface of the second trench via the pinninglayer, and the light shielding layer may be formed so as to bury theinner portion of the second trench via the pinning layer and theinsulating film.

(4) In the solid-state imaging device described in (1), the solid-stateimaging device may further includes an insulating film that is formed soas to cover the inner surface of the second trench via the pinninglayer, the pinning layer may be formed so as to cover the inside surfaceof the first trench, the insulating film may be formed so as to bury theinner portion of the first trench via the pinning layer, and the lightshielding layer may be formed so as to bury the inner portion of thesecond trench via the pinning layer and the insulating film.

(5) In the solid-state imaging device described in any one of (1) to(4), the pinning layer may be formed of a material which includes anegative fixed charge.

(6) In the solid-state imaging device described in any one of (1) to(5), the pinning layer may be formed by using hafnium oxide, tantalumpentoxide, or aluminum oxide.

(7) In the solid-state imaging device described in any one of (1) to(6), the light shielding layer may be formed by using aluminum ortungsten.

(8) In the solid-state imaging device described in any one of (1) to(7), the solid-state imaging device may further include a pixeltransistor that is provided on a surface of a side opposite to theincident surface in the semiconductor substrate and outputs a signalcharge generated by the photoelectric conversion portion as an electricsignal, and a wiring layer that is provided so as to cover the pixeltransistor in the surface of the side opposite to the incident surfacein the semiconductor substrate.

(9) In the solid-state imaging device described in any one of (1) to(8), the solid-state imaging device may further include a color filterthat transmits the incident light to the light sensing surface, whereina plurality of kinds of filter layers having a high transmissivity tolight of wavelength ranges different from one another may be disposed soas to be adjacent to one another corresponding to each of the pluralityof pixels in the color filter, and the trench in a periphery of thepixel P, in which a filter layer having higher transmissivity withrespect to light of the wavelength range of the longest wavelength inthe plurality of kinds of filter layers is positioned, among theplurality of pixels P may be formed so as to be deeper than the trenchesin other portions.

(10) According to another embodiment of the present disclosure, there isprovided a method of manufacturing a solid-state imaging deviceincluding providing a plurality of photoelectric conversion portionswhich receive incident light through a light sensing surface so as tocorrespond to a plurality of pixels in a semiconductor substrate, andforming a pixel separation portion, which electrically separates theplurality of pixels, between the plurality of pixels in an inner portionof the semiconductor substrate, the forming of the pixel separationincludes providing at least a pinning layer and a light shielding layerin an inner portion of a trench which is provided on a side portion ofeach of the photoelectric conversion portions in an incident surfaceside of the semiconductor substrate into which the incident lightenters, a first trench and a second trench having a width wider thanthat of the first trench in a portion shallower than the first trench inthe semiconductor substrate are formed as the trench, the pinning layeris formed so as to cover an inner portion of the first trench and aninside surface of the second trench, and the light shielding layer isformed so as to bury an inner portion of the second trench at least viathe pinning layer.

(11) According to still another embodiment, there is provided anelectronic apparatus including a plurality of photoelectric conversionportions each provided to correspond to each of a plurality of pixels ina semiconductor substrate and receives incident light through a lightsensing surface, and a pixel separation portion that is provided betweenthe plurality of pixels in an inner portion of the semiconductorsubstrate and electrically separates the plurality of pixels, wherein atleast a pinning layer and a light shielding layer that are provided inan inner portion of a trench which is provided on a side portion of eachof the photoelectric conversion portions in an incident surface side ofthe semiconductor substrate into which the incident light enters, thetrench includes a first trench and a second trench having a width widerthan that of the first trench in a portion shallower than the firsttrench in the semiconductor substrate, the pinning layer is formed in aninner portion of the first trench so as to cover an inside surface ofthe second trench, and the light shielding layer is formed so as to buryan inner portion of the second trench at least via the pinning layer.

Moreover, in the above-described embodiments, the photodiode 21 is anexample of the photoelectric conversion portion. In addition, in theabove-described embodiments, the camera 40 is an example of the electricapparatus.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An imaging device, comprising: a semiconductorsubstrate including a first side as a light-incident side and a secondside opposite to the first side; a plurality of photoelectric conversionportions disposed in the semiconductor substrate; a trench disposedbetween adjacent photoelectric conversion portions of the plurality ofphotoelectric conversion portions, the trench including: a first portionincluding a first film including hafnium oxide, tantalum pentoxide oraluminum oxide, a second portion including the first film and aninsulating film disposed on the first film, and a silicon oxide filmdisposed between the semiconductor substrate and the first film in thefirst portion, wherein, a width of the first portion is smaller than awidth of the second portion in a cross-section view.
 2. The imagingdevice according to claim 1, wherein the insulating film is in directcontact with the first film in the second portion.
 3. The imaging deviceaccording to claim 1, wherein the first film is selected from the groupconsisting of hafnium oxide, zirconium dioxide, aluminum oxide,neodymium oxide, tantalum pentoxide, lanthanum oxide, praseodymiumoxide, promethium oxide, samarium oxide, europium oxide, gadoliniumoxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide,thulium oxide, ytterbium oxide, lutetium oxide or yttrium oxide, andcombinations thereof.
 4. The imaging device according to claim 1,further comprising: a pixel including at least one of the photoelectricconversion portions and a pixel transistor, wherein the pixel transistorand a wiring layer are disposed at the second side of the semiconductorsubstrate, wherein the first portion is disposed closer to the secondside of the semiconductor substrate than the second portion.
 5. Theimaging device according to claim 4, wherein the pixel transistorincludes at least a reset transistor, an amplification transistor, and atransfer transistor.
 6. The imaging device according to claim 1, whereina light-shielding portion is disposed corresponding to the trench. 7.The imaging device according to claim 1, wherein at least one of thephotoelectric conversion portions includes a hole accumulation diodestructure.
 8. The imaging device according to claim 1, wherein athickness of the insulating film is 5 μm or less.
 9. The imaging deviceaccording to claim 1, wherein the first film comprises hafnium oxidethat extends outside of the trench to a surface of the semiconductorsubstrate.
 10. The imaging device according to claim 1, wherein thetrench has a lattice shape in a plan view.
 11. The imaging deviceaccording to claim 1, wherein the insulating layer is in direct contactwith an entirety of an inner side of the first film in the secondportion.
 12. The imaging device according to claim 11, wherein athickness of the insulating film is 5 μm or less.
 13. The imaging deviceaccording to claim 2, wherein the first film is selected from the groupconsisting of hafnium oxide, zirconium dioxide, aluminum oxide,neodymium oxide, tantalum pentoxide, lanthanum oxide, praseodymiumoxide, promethium oxide, samarium oxide, europium oxide, gadoliniumoxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide,thulium oxide, ytterbium oxide, lutetium oxide or yttrium oxide, andcombinations thereof.
 14. The imaging device according to claim 13,wherein the pixel transistor includes at least a reset transistor, anamplification transistor, and a transfer transistor.
 15. The imagingdevice according to claim 13, wherein a thickness of the insulating filmis 5 μm or less.
 16. The imaging device according to claim 13, whereinthe first film comprises hafnium oxide that extends outside of thetrench to a surface of the semiconductor substrate.
 17. The imagingdevice according to claim 5, wherein a light-shielding portion isdisposed corresponding to the trench.
 18. The imaging device accordingto claim 5, wherein at least one of the photoelectric conversionportions includes a hole accumulation diode structure.
 19. The imagingdevice according to claim 5, wherein the imaging device receives anincident light from an optical system.
 20. The imaging device accordingto claim 5, wherein the imaging device sends a signal to a signalprocessing portion.